supermobsx task error

[19:13:48] [Server thread/WARN]: [SuperMobsX] Task #838 for SuperMobsX v1.3.0 generated an exception
java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.7.0_51]
	at java.util.ArrayList$Itr.next(Unknown Source) ~[?:1.7.0_51]
	at supermobsx.snakes.SnakeMain$1.run(SnakeMain.java:60) ~[?:?]
	at org.bukkit.craftbukkit.v1_7_R1.scheduler.CraftTask.run(CraftTask.java:53) ~[craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]
	at org.bukkit.craftbukkit.v1_7_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:345) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:587) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]
	at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]
	at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]
	at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617) [craftbukkit.jar:git-Bukkit-1.7.2-R0.3-2-g85f5776-b3023jnks]